The winding form of a coil provided in a stator of a rotary electric machine can be roughly classified into a “concentrated winding” and a “distributed winding”. The concentrated winding has a structure in which windings are wound together around one tooth of a stator core. The concentrated winding stator is simple in the coil form and has a short coil end as compared to the stator distributed winding. However, since the rotating magnetic field generated by the concentrated winding stator is a rectangular wave, vibration or noise due to the harmonic components is relatively large. On the other hand, the distributed winding has a structure in which windings are wound across a plurality of teeth of the stator core. In the distributed winding stator, since coils of different phases are overlapped to each other in the radial direction and the axial direction outside the stator core, a coil end is larger as compared to the concentrated winding stator. However, since the rotating magnetic field generated by the distributed winding stator is close to a sine wave, vibration or noise is smaller, and the output property of the rotary electric machine is superior to the case of the concentrated winding.
In consideration of such difference in characteristics, the distributed winding stator is adopted in many cases to realize a rotary electric machine with small vibration and noise (with high Noise Vibration (NV) property). Further, in order to reduce the harmonic components of a rotating magnetic field generated by the distributed winding stator and to make the rotating magnetic field closer to a sine wave, it is considered that windings of different phases are provided in the same slot of a stator as in a motor disclosed in JP-A-2001-186736 (FIG. 1).
It is considered that the rotating magnetic field generated by the stator having the windings of different phases in the same slot as described above has sine waves different in the degree of approximation from each other in a radial cross-section depending on distribution of the winding of each phase. Accordingly, it is advantageous that the winding of each phase is distributed so as to realize a rotating magnetic field close to a sine wave with small harmonic components.
Accordingly, an aspect of the present invention provides a stator for a rotary electric machine capable of reducing a harmonic component of a rotating magnetic field.
(1) According to an embodiment of the present invention, there is provided a stator for a rotary electric machine. The stator includes:
a stator core (e.g., a stator core 11 in an embodiment to be described below) including a plurality of teeth (e.g., teeth 14 in the embodiment) arranged along a circumferential direction and a plurality of slots (e.g., slots 15 in the embodiment) formed between the teeth adjacent to each other; and
multi-phase coils in which windings (e.g., fine wire bundles 12 in the embodiment) of different phases are respectively wound around the teeth by distributed winding,
wherein each of the slots is provided therein with a plurality of windings forming the coils, and
wherein the plurality of windings of the different phases are arranged to be overlapped in the circumferential direction in at least a part of the plurality of slots.
(2) In the stator of (1), the coil of each phase includes:                a first loop (e.g., a first loop Lul1 in the embodiment) for winding around a first number of the teeth, the first loop being formed between one side in the circumferential direction of a first slot (e.g., a first slot Sul1 in the embodiment) as a starting end and the other side in the circumferential direction of a second slot (e.g., a second slot Sul2 in the embodiment) located to interpose the first number of the teeth from the first slot toward the other side;        a second loop (e.g., a second loop Lul2 in the embodiment) for winding around a second number of the teeth, the second loop being formed to be continuous from a terminal of the first loop between a third slot (e.g., a third slot Sul3 in the embodiment) separated by one tooth from the first slot toward the one side in the circumferential direction and a fourth slot (e.g., a fourth slot Sul4 in the embodiment) located to interpose the second number of the teeth from the third slot toward the one side; and        a third loop (e.g., a third loop Lul3 in the embodiment) for winding around the first number of the teeth, the third loop being formed to be continuous from a terminal of the second loop between the other side in the circumferential direction of a fifth slot (e.g., a fifth slot Sul5 in the embodiment) separated by one tooth toward one side from the third slot and the one side of a sixth slot (e.g., a sixth slot Sul6 in the embodiment) located to interpose the first number of the teeth from the fifth slot toward the one side, wherein a relation that the second number=the first number+2 is satisfied,and        
wherein a terminal of the third loop is connected to the starting end of the first loop or is a terminal of the coil.